Health experts on Monday said they were troubled by the recent resurgence in syphilis in the United States, especially among gay and bisexual men. The researchers, citing studies presented at the 2004 National STD Prevention Conference in Philadelphia, are worried that many Americans, especially gay and bisexual men and adolescents, are tuning out safer sex messages. Researchers also reported high rates of the human papillomavirus and chlamydia, another common venereal infection, and other sexually transmitted diseases among some groups. "STDs can cause serious medical consequences, including infertility, transmission to newborns, neurologic damage, and increased risk of HIV transmission," said Ronald Valdiserri, deputy director of HIV, STD and Tuberculosis prevention programs at the Centers for Disease Control and Prevention. "While we acknowledge the successful declines in herpes, overall STD rates in the U.S. remain alarmingly high."

The prevalence of herpes simplex virus type 2, the most common cause of genital herpes, declined to 17.6% among those aged 14 to 49 in the 1999-2000 period from 21.3% in the 1988-1994 period, according to data from two CDC surveys. The prevalence of the incurable virus fell 74% among those aged 14 to 19.

But a rising number of syphilis infections in men, particularly among those who are gay or bisexual, helped fuel a rise in the nation's syphilis rate in 2003, according to preliminary data released by the CDC. Last year, there were 7,082 confirmed cases of primary and secondary syphilis, the initial stages of the disease, compared with 6,862 cases in 2002, according to the data. The rate of syphilis rose to 2.5 cases per 100,000 people from 2.4 cases per 100,000 in 2003. CDC researchers estimate that 60% of the cases occurred among men who had sex with men, compared with 5% in 1999. The resurgence of the disease in that high-risk group is of particular concern because of its links to the HIV. Studies have shown that syphilis and other STDs increase the likelihood of HIV infection. Up to 70% of gay and bisexual men infected in recent syphilis outbreaks in the United States were HIV positive. In addition to helping spread HIV, untreated syphilis can cause arthritis, heart disease, insanity, and death as well as miscarriages, stillbirths, and severe infections in newborn babies.